Image forming apparatuses can be used to print an image on a printing medium, such as paper, for example, based on input image signals. Examples of image forming apparatuses include printers, copiers, facsimiles and so-called multifunctional apparatuses that combine some of the functionalities of the aforementioned apparatuses.
An image forming apparatus can use various image formation methods including, for example, an electro-photographic method and an inkjet method. In such methods, toner or ink can adhere to paper to form a visible image on the paper. The image forming apparatus includes a paper supply unit to supply paper, a printing unit to apply toner or ink to the paper to form an image in accordance with the image formation method being used, and a paper discharge unit to discharge the paper on which the image is printed to the outside.
More particularly, the paper supply unit can be a paper supply cassette, which includes a paper loading plate on which paper to be supplied is loaded, and a lifting device to move the paper loading plate upward toward a pickup roller. The paper loaded on the paper loading plate is picked up one sheet at a time via the pickup roller to be delivered to the printing unit.
To allow the pickup roller to continuously pick up the paper loaded on the paper loading plate when using the lifting device, it may be necessary to increase the distance that the paper loading plate moves upwards as the amount of the paper loaded on the paper loading plate is reduced. The lifting device can be realized in such a manner that the paper loading plate is moved up and down using a motor or an elastic force, e.g., of a spring.